试验采用三因素五水平最优回归设计,研究高产优质苋菜(Amaranthus)的合理施肥问题.建立了氮磷钾肥用量与苋菜产量,硝酸盐含量关系的平方多项式与平方根多项式回归方程.应用频率分析方法得到兼顾苋菜高产和低硝酸盐含量的最佳氮磷钾用量(公斤/亩)组合:N,13.0—13.5;P_2O_5,5.5—6.0;K_2O,12.5—13.0. The optimal three-factor and five-level regression design was used to study the reasonable fertilization of high-yield and high-quality Amaranthus tuberosus L. The square polynomial and square-root polynomial regression equations were established for the relationship between the yield of NPK and the yield of nitrate, and the square root polynomial regression equation.Using frequency analysis The optimal combinations of nitrogen, phosphorus and potassium (kg / acre) for both high yield and low nitrate content of amaranth were obtained: N, 13.0-13.5; P_2O_5,5.5-6.0; K_2O, 12.5-13.0.